The present disclosure relates to a method capable of easily checking a defect of a battery pack.
Recently, secondary batteries that are chargeable and dischargeable are being widely used as energy sources for wireless mobile devices. Also, the secondary batteries have attracted considerable attention as power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (Plug-In HEVs), which have been proposed as solutions to air pollution and the like caused by existing gasoline and diesel vehicles that use fossil fuels.
Small sized mobile devices use one or a couple of battery cells for each device. On the other hand, medium and large sized devices such as vehicles use a battery module in which a plurality of battery modules are modularized, or a battery pack in which a plurality of battery modules are electrically connected to each other, due to requirement for high power and large capacity.
It is preferable to manufacture the medium and large sized battery module or the battery pack as small and lightweight as possible. Therefore, prismatic and pouch type batteries, which are capable of being charged at a high degree of integration and are relatively lightweight compared to their capacities, are being mainly used as a battery cell (a unit battery) of the medium and large sized battery module and battery pack. Particularly, much interest is recently focused on the pouch type batteries, which use an aluminum laminate sheet as an exterior member, due to their advantages such as light weight, low manufacturing costs, and easy modification of the shapes.
The battery cells constituting the medium and large sized battery module or battery pack are constituted by secondary batteries that can be charged and discharged, so that such high power and large capacity secondary batteries may generate a large amount of heat. Particularly, since the laminate sheet of the pouch type battery is coated with a polymer material having low thermal conductivity, it is difficult to effectively cool a temperature of the entire battery cell.
When the heat of the battery module, which is generated during the charge and discharge processes, is not effectively removed, the heat may be accumulated, consequently accelerating degradation of the battery cell and causing ignition or explosion in some cases. Therefore, a cooling system is needed in the high power and large capacity battery module or battery pack so as to cool the battery cells contained in the high power and large capacity battery module or battery pack.
Also, a quality test is performed before the medium and large sized battery packs are delivered.
The quality test includes inspecting defects that may occur within the battery pack manufactured at a high degree of integration. For example, the defects include a leakage defect in which an electrolyte or a gas leaks from the battery cells constituting the battery pack, a leakage trouble in which a refrigerant leaks from the cooling system, and a case in which the pack housing is damaged.
In the related art, an operator visually checks each of the battery cells, the pack housing, and the cooling system to inspect one by one whether defects occur. However, this procedure is not only time-consuming but also less accurate, so a defect, which was not found during the inspecting process, may be present in the battery pack even after the delivery.
Thus, there is great need for technologies that may solve the above-described limitations.